Printed circuit boards are becoming increasingly complex with an increasing number of components and interconnections. If a single part on the board becomes defective, it is often more cost effective to rework the board by replacing the damaged component(s) instead of replacing the entire board. In order to provide a quality reworked board, the component must be removed and reattached to the PC board without damaging the PC board or nearby components.
A past solution used for both removal and attachment of integrated circuit components on a printed circuit (PC) board is a laser rework station, such as the Laser Series 100 SMT Rework Station. Using a rework station, a PC board is placed inside the rework station and the area on the board where the component is to be attached or removed is defined by the rework station technician. To attach a component, a laser beam emanating from the rework station is focused on the package perimeter, repetitively moving around the perimeter of the component in the vicinity of the leads, until a temperature above the solder melting point is reached, thereby attaching the component leads to the PC board.
One problem with the laser rework station is its expense. Prices for the laser rework station typically run in the hundreds of thousands of dollars. Because of this relatively high cost, it is prohibitive to have a rework station at the work area of each rework technician. Frequently, a rework floor will own only one rework machine because of its expense. Further, because of their complexity, rework stations are often down. Therefore, if the rework machine is down, either a bottleneck will occur or rework operators must perform rework manually using conventional soldering techniques.
However, the main problem with the rework station is not its expense but the damage that it causes to the IC components it is trying to attach. Assemblies are routinely damaged due to excessive heat applied during the preheat state of the rework station. Obviously attaching a damaged part, only adds to the time and expense of reworking the board since the damaged part must be removed and replaced with a functional part in order for the printed circuit board to be functional.
The conventional method for reworking a component is by soldering the component onto the PC board by using a soldering iron, such as the Metcal SMT Rework Iron. The problem with using a soldering iron to reattach a component to a PC board is that attachment takes a long time since the rework technician must solder one lead of the component to its corresponding PC board pad at a time. Further, using a soldering iron to attach individual leads to the component to the PC board increases the probability of damage to the leads and the board. During rework using a soldering iron, the component leads and the PC board would be routinely damaged due to the soldering iron tip making physical contact in order to solder the component to the PC board.
A method used for removing a ceramic part is by use of a hot air device, such as a Weller hot air pencil. Typically, the hot air jet device is attached to a stationary structure or boom overhead of the component to be removed. Typically, this process is used for removal for of ceramic components, such as a capacitor. When the hot air flow is initiated, heat is transferred from the heated component to the component leads attached to the component causing the solder to flow. When the solder is molten, the rework technician can remove the part. Because the ceramic component is being removed, any damage caused to the part is not problematic.
A method of efficiently attaching components, including integrated circuit SMT components, to a printed circuit board without causing undue damage to the parts or board is needed.